I agree about the bound & stretched out position. Very sexy.
But I personally would like to see more ripped body/big titted girls, or even FBB, because they are more fit to 'fight' the tentacles or plants, which would make it hotter.
There's a great scene with Richelle Ryan bound & stretched getting fucked by a machine: you can literally see how she's trying to control her belly muscles while she's getting fucked, but in the end she is losing all control to the point of orgasm.
I would love to see that kind of scene being made with that kind of woman, getting fucked in alle holes by tentacles or plants.